CSS ทำอย่างไร ถ้ากำหนด block สูง 50px ต้องการให้ข้อความข้างในอยู่ตรงกลางเป๊ะๆ

<div id="t3">
<ul>
<li id="header">
<p><span id="list">ลำดับ</span><span id="topic">หัวข้อ</span><span id="name">ผู้ตั้งกระทู้</span><span id="reply">ตอบ</span><span id="read">อ่าน</span><span id="last">ตอบครั้งล่าสุด</span></p>
</li>
<li id="content">
<a href="1.html" itemprop="url">
<p><span id="list">1</span>
 <span id="topic">test</span>
    <span id="name">B1</span>
 <span id="reply">0</span>
    <span id="read">0</span><span id="last">today</span></p>
</a>
</li>
</ul>
</div>

#t3 * {
	border:1px solid #000;
	margin: 0 auto;
	width:610px;
	text-align:center;
    float:left;
    padding:0;
}
#t3 ul li {
	list-style-type: none;
	padding: 0.5em 0;
	border-bottom: solid 1px #f8f8f8;
}
#t3 ul li:first-child {
	border-top: solid 3px #333333;
	border-bottom: solid 1px #333333;
}
#t3 ul li:last-child {
	border-bottom: solid 1px #333333 !important;
}
#t3 ul li#header {
	width: 100%;
	font-weight: bold;
}

#t3 ul li#header p span#list {
	width: 5%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#header p span#topic {
	width: 40%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#header p span#name {
	width: 15%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#header p span#reply {
	width: 10%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#header p span#read {
	width: 10%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#header p span#last {
    width: 18%;
	padding: 1px auto;
	border:solid 1px #000;
}

#t3 ul li#content *{
	width: 100%;
    height:50px;
}
#t3 ul li#content span#list {
	width: 5%;
	padding: 1px auto;
	border:solid 1px #000;
    display: table-cell;
    text-align: center;
    vertical-align: middle;
}
#t3 ul li#content p span#topic {
	width: 40%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#content p span#name {
	width: 15%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#content p span#reply {
	width: 10%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#content p span#read {
	width: 10%;
	padding: 1px auto;
	border:solid 1px #000;
}
#t3 ul li#content p span#last {
	width: 18%;
	padding: 1px auto;
	border:solid 1px #000;
}